The present invention relates to a drive apparatus for a drill stem, in particular for de-coking systems.
In oil refineries, the last otherwise unusable fraction of the crude oil is transformed into coke. This transformation is performed by feeding this fraction into drums which are filled with coke as the operation proceeds. Once the maximum filling level of the drums has been reached, the coke is cut out from the drums.
This so-called “de-coking” is usually carried out using high-pressure water jets which disintegrate the coke and wash it out of the drums. The tool for generating these high-pressure water jets is inserted into the drums from the top using a drilling rig. The subject of the present invention is in particular the construction of the drill stem drive and therefore the transition from the water supply to the drill stem.
In prior art generic systems, this transition from the water supply to the drill stem is formed as an integral feeder. The first, top end is connected to a water supply via a flange. The second, bottom end of the feeder is connected to the flange of the drill stem. This second, bottom end is usually supported in thrust and journal bearings in order to ensure smooth rotation. At the second end of the feeder there is also a gear box which causes the drill stem to rotate in operation. The water supply, the feeder and the drill stem are connected in an aligned and liquid-tight fashion so that a tool attached to the free end of the drill stem for de-coking is supplied with the requisite water in an operating state.
In the area of the feeder, the sealing rings, which are positioned at the transition between stationary and rotating structural elements, are particularly subject to wear and tear and must be replaced at regular intervals. Wear and tear shows at the first end of the feeder, where a fluid-tight connection is to be established to the water supply and at the same time fixed and rotating parts of the drive apparatus are adjacent to each other. In prior art systems, the sealing rings acting as sealing elements at the transition between fixed and rotating structural parts must be replaced in the steel frame of the de-coking system while the drill stem drive is in place, which contributes to maintenance overhead.